High current switch arrangement for quick break



A ril 7, 1964 F. KESSELRING 3,

HIGH CURRENT SWITCH ARRANGEMENT FOR QUICK BREAK Filed Jan. 27, 1960 INVEN TOR. F B/ 7' Z KEJJA-Z E/N 0; 7190A 8M6, 51 3278, 623215 3 fa /em 14770,49! 7f Patented Apr. 7, 1964 3,128,361 HIGH CURRENT SWITCHARRANGEMENT FOR QUICK BREAK Fritz Kesselring, Kusnacht, Zurich,Switzerland, assignor to Siemens-Schuckertwerke A.G., Berlin, Germany, a

corporation of Germany Filed Jan. 27, 1960, Ser. No. 5,066 Claimspriority, application Germany Feb. 17, 1959 2 Claims. (Cl. 2.00-151)This invention relates to a high speed circuit breaker having a highvoltage rating and is more specifically directed to a high speed, highvoltage circuit breaker of the electrodynamic type.

Electrodynamic circuit breakers are well known in the art and aredescribed, for example, in copending application Serial No. 558,349,filed January 10, 1956, now Patent No. 2,951,188 entitled High SpeedContacting Device, and in US. Patent No. 2,916,579 to Kesselring et al.

The electrodynamic concept for the operating means of a circuit breakerresults in extremely high speed circuit interruption whereby therecovery voltage during interruption at any instant is insufliicent tocause a breakdown over the distance between the movable and stationaryelements.

In the past, the electrodynamic circuit breaker has had applicationmainly in connection with low voltage circuits. In using this conceptfor high voltage circuits several problems arise. The most important ofthese problems is that the stationary contacts must be sufficientlyspaced from one another to prevent breakdown or restriking of the arcwhen the circuit breaker or interrupter is in its open position. Becauseof this and where the movable contact is of the bridging type, the massof the movable contact is substantially increased since it must spanthis relatively large distance between the stationary contacts.Furthermore, the movable contact must retain the same current carryingcross-sectional area to prevent too high a temperature rise duringnormal operating conditions.

This increase in mass results in a smaller acceleration for a givenapplied operating energy and could, therefore, prevent the applicationof such a switching device to high voltage application.

The principle of the present invention is to provide a high speed highvoltage circuit breaker which operates on the electrodynamic principlewherein the movable contact is carried in an elongated insulating memberwhich is interposed between the stationary contacts which are bridged bythe movable contact. This insulating barrier will, therefore, beinterposed between the stationary contacts when the movable contact ismoved to its open position and accordingly the stationary contacts maybe more closely spaced than if the only dielectric between thestationary contacts were air. By way of example, typical commerciallyavailable solid insulat ing materials can be used for the insulatingsheet which have a dielectric strength ten or more times greater thanthe dielectric strength of air at atmospheric pressure.

Since the stationary contacts may be more closely spaced to one anotherby practicing the present invention, the distance which the movablecontact must now span is substantially decreased. Furthermore, since themovable contact will generally have a small current carrying area inorder to decrease its mass, its resistance is relatively high, but sincethe span of the contact is shorter, the net resistance introduced intothe circuit by the movable contact is relatively lower so that thetemperature increase of the circuit breaker may be decreased.

It is to be noted that the net decrease in the mass of the movablecontact is greater than the required increase in mass for the insulatingfollower construction. However, even in applications where there is nonet saving in mass it will be apparent that the overall size of theinterrupter is considerably decreased and the highly advantageousinsulating barrier which is interposed between the stationary contactsstill applies.

In operation the insulating barrier may have a portion thereof connectedto a short circuited winding which in turn is coupled to an operatingwinding. When the operating winding is energized, an extremely highcurrent will be induced in the short circuited winding whereby the shortcircuited winding and the insulating barrier which carries the movablecontact will be accelerated toward the circuit breaker open position inthe usual manner.

Accordingly, the primary object of this invention is to provide a novelhigh speed, high voltage circuit break- Another object of this inventionis to provide a novel high voltage circuit breaker using theelectrodynamic operating principle.

A further object of this invention is to provide a novel high voltagecircuit breaker which operates on the electrodynamic principle andutilizes an insulating follower for carrying the movable contact,whereby the insulating follower is interposed between a pair ofstationary contacts.

A further object of this invention is to provide a novel high voltagecircuit breaker wherein the movable contact is carried by an insulatingsheet which is moved to a position interposed between a stationarycontact and other points of different potential.

Yet a further object of this invention is to provide a novel insulatingmember for carrying the movable contact of an electrodynamic circuitbreaker whereby the mass of the movable contact is substantiallydecreased.

These and other objects of this invention will become apparent from thefollowing description when taken in connection with the drawings inwhich:

FIGURE 1 shows a side cross-sectional view of a preferred embodiment ofthe present invention.

FIGURE 2 shows a top plan view of FIGURE 1. 7

FIGURE 3 shows a side view of a second embodiment of a contact which canbe used for the movable contact in the switch of FIGURE 1.

Referring now to FIGURES 1 and 2, the circuit breaker of the inventionis comprised of a first and second stationary contact 1 and 2,respectively, which are connected in a circuit to be protected (notshown) in any desired manner. A bridging movable contact 3 has aprismatic cross-section and is elongated along the tapered contactingsurface of the stationary contacts 1 and 2 bridges stationary contacts 1and 2 as shown. The movable contact 3 is carried by U-shaped insulatingsheets 4 and 5 wherein the bottom legs of the U of the sheets arefastened by cementing and a slot is placed in this common bottom leg toaccept movable contact 3. More specifically, a flexible strip ofmaterial 6, which could be of rubber, is cemented to the top of contact3 as is shown in FIGURE 1, and this assembly of contact 3 and flexiblestrip 6 is thereafter inserted in the slot in U-shaped insulating strips4 and 5 to be held therein by friction or cementing or any other desired'manner. If desired, strips 4 and 5 could be an integral member whichcould be extruded to proper shape.

The U-shaped strips -4 and 5, which comprise the insulating follower ofthe invention, are preferably formed to envelop either end of stationarycontacts 1 and 2 as is best seen in FIGURE 2 and have their lower endrigidly connected in any desired manner to a short circuited winding 7which may be a flat disc of conductive material such as copper oraluminum. The disc 7 is normally supported by an insulating block 8which is secured to some relatively fixed member and has an operatingwinding 9 embedded therein.

The circuit for energizing operating winding 9 may be derived from faultsensing elements associated with the circuit being protected as in themanner shown in above noted cope-nding application Serial No. 558,349 orby any method in accordance with the well-known principles ofelectrodynamic circuit breakers. When winding 9 is energized, anextremely high circulating current will be induced in short circuitedwinding 7. Since windings 7 and 9 are very closely coupled to oneanother, the magnetic fields generated by these windings will beextremely high and will repel one another with very great force. Thiswill impart an extremely high acceleration to the disc 7 and theinsulating strips 4 and and low mass movable contact 3 associatedtherewith in a vertical direction so that the movable contact 3 is movedto an upper, and contatc disengaged position, in an exceedingly shorttime.

In order to provide a contact engaging force and at the same timeprovide means for retaining the movable structure in its disengagedposition when it is moved from the engaged position of FIGURE 1 to anupper and disengaged position, a pair of spring operated mechanisms 10and 11 is carried on stationary contacts 1 and 2, respectively. Springmechanisms 10 and 11 are identical and are shown in FIGURE 1 for thecase of mechanism 10. Thus, mechanism 10 is comprised of an insulatinghousing 12 which has a central bore therein for carrying a com p-ressionspring 13. The compression spring 13 operates a plunger .14 which bearson an output link 15 which is pivoted at a relatively fixed pivot 16. Asimilar output link 17 is provided for spring mechanism 11 as shown inFIGURES 1 and 2. Each of the output links 15 and 17 bears directly uponthe top of insulating members 4 and 5 to bias them downwardly to therebydrive movable contact 3 into high pressure contact engagement withstationary contacts 1 and 2.

At the same time members 15 and 17 will operate to hold insulatingmembers 4 and 5 in an upward position when the movable switch structureis moved upwardly to a disengaged position.

Thus, when the movable contact structure is accelerated upwardly, thespring arms 15 and 17 are first cammed apart during the initialextremely high force created by disc 7 and operating winding 9 which areclosely coupled. As the movable structure moves upwardly and thecoupling between windings 7 and 9 decreases and the force on the movablestructure decreases until, when the movable contact assumes an upwardlydisplaced disengaged position, the force decreases to zero. At thispoint the arms 15 and '17 which are driven into relatively frictionalforce engagement with insulating members 4 and 5 by their respectivebiasing springs will retain the movable contact structure in thisupwardly displaced disengaged position.

In order to reclose the switch, it is only necessary to push the top ofinsulating members 4 and 5 downwardly to overcome the frictional forceexerted by spring bias arms 15 and 17 until the movable structureresumes the position of FIGURE 1 and the circuit breaker is closed.

In operation it will be apparent that as the movable contact moves toits disengaged position it is followed by a solid sheet of insulatingmaterial which is interposed between stationary contacts 1 and 2. Thissolid dielectric barrier which can completely fill the gap betweencontacts 1 and 2 and slide between either adjacent stationary contactsurface permits a very close spacing of contacts 1 and 2. This reducesthe span of movable contact 3 to a minimum, and accordingly, its mass isreduced to a minimum. Furthermore, by forming insulating members 4 and 5with a U-shaped cross-section the creepage distance, as best seen inFIGURE 2, between contacts 1 and 2 is substantially increased.

In a typical application of the device of FIGURES 1 and 2, the circuitbeing protected was rated at 10,000

volts at 1,000 amperes. The weight of the movable contact 3 was 1.8grams, and the total Weight of the movable system not including disc 7was approximately 40 grams. The closing contact pressure from links 15and 17 was 20 kilograms to give a contact resistance of 20 microohms.With this construction, the temperature rise in the movable contact wasfound to be 2 C. higher than the temperature of the stationary contacts1 and 2. The operating time for this type of circuit breaker was foundto be a fraction of a millisecond.

The shape of the movable contact 3 may, of course, assume many forms.For example, in FIGURE 3 the movable contact is illustrated as beingformed of a plurality of segments 18 cemented to a common plate 19 whichmay be of rubber which serves the purpose of plate 6 of FIGURE 1 as wellas to provide a common support for segments 18. With this type ofarrangement, the contact resistance was found to be decreased from 20microohms for the solid movable contact of FIGURE 1 to approximately 10micro-ohms.

It is to be noted that, because of the small length of the movablecont-act, made possible by the close spacing of stationary contacts 1and 2, the resistance of the movable contact may be reduced to valuescomparable to the contact resistance whereby the net resistance of thecontact arrangement is reduced and the temperature rise is correspondin'gly reduced.

If desired, parallel circuit means could be provided for stationarycontacts 1 and 2 such as a resistor 20, shown in dotted lines in FIGURE1, which will reduce the rate of rise of recovery voltage duringinterrupting conditions. A switching means may be connected in serieswith resistor 15 to achieve final circuit interruption of the currentflow therethrough. If desired, the resistor 15 could be replaced by afuse which would operate first as a low resistor to control the recoveryvoltage across contacts 1 and 2 and thereafter serve as a finalinterrupting means for the circuit.

In the foregoing the invention has been described only in connectionwith preferred embodiments thereof. Many variations and modifications ofthe principles of the invention within the scope of the descriptionherein are obvious. Accordingly, it is preferred to be bound not by thespecific disclosure herein but only by the appended claims.

What is claimed is:

1. A high voltage circuit breaker; said high voltage circuit breakercomprising a pair of stationary contacts positioned in spaced relationwith respect to one another and a movable bridging contact; an operatingmeans for said movable bridging contact; said operating means beingoperable to move said movable contact between an engaged and disengagedposition; said operating means being a high speed operating meansoperable to move said bridging contact to said contact disengagedposition at a speed whereby recovery voltage at any instant isinsufficient to cause breakdown from said movable contacts to saidstationary contacts; and an insulating barrier means; said insulatingbarrier means being interposed between said pair of stationary contactswhen said movable bridging contact is moved to said disengaged position;said pair of stationary contacts being relatively closely spaced withrespect to one another relative to their required spacing in the absenceof said insulating barrier whereby the mass of said movable contact isdecreased; said movable bridging contact being carried by saidinsulating barrier; a spring biasing means; said spring biasing meansbeing operatively connected to said insulating barrier for biasing saidmovable contact toward said engaged position and for providing contactpressure; said spring biasing means being characterized in having itsbiasing force sharply decreased to zero immediately after movement ofsaid movable bridging contact toward its said disengaged position.

2. A high voltage circuit breaker; said high voltage circuit breakercomprising a pair of stationary contacts positioned in spaced relationwith respect to one another and a movable bridging contact; an operatingmeans for said movable bridging contact; said operating means beingoperable to move said movable contact between an engaged and disengagedposition; said operating means being a high speed operating meansoperable to move said bridging contact to said contact disengagedposition at a speed whereby recovery voltage at any instant isinsuificient to cause breakdown from said movable contacts to saidstationary contacts; and an insulating barrier means; said insulatingbarrier means being interposed between said pair of stationary contactswhen said movable bridging contact is moved to said disengaged position;said pair of stationary contacts being relatively closely spaced withrespect to one another relative to their required spacing in the absenceof said insulating barrier whereby the mass of said movable contact isdecreased; said movable bridging contact being carried by saidinsulating barrier;

a biasing means; said biasing means being operatively connected to saidinsulating barrier for biasing said movable contact toward said engagedposition and for providing contact pressure; said biasing means beingcharacterized in having its biasing force sharply decreased to Zeroimmediately after movement of said movable bridging contact toward itssaid disengaged position.

References Cited in the file of this patent UNITED STATES PATENTS

1. A HIGH VOLTAGE CIRCUIT BREAKER; SAID HIGH VOLTAGE CIRCUIT BREAKERCOMPRISING A PAIR OF STATIONARY CONTACTS POSITIONED IN SPACED RELATIONWITH RESPECT TO ONE ANOTHER AND A MOVABLE BRIDGING CONTACT; AN OPERATINGMEANS FOR SAID MOVABLE BRIDGING CONTACT; SAID OPERATING MEANS BEINGOPERABLE TO MOVE SAID MOVABLE CONTACT BETWEEN AN ENGAGED AND DISENGAGEDPOSITION; SAID OPERATING MEANS BEING A HIGH SPEED OPERATING MEANSOPERABLE TO MOVE SAID BRIDGING CONTACT TO SAID CONTACT DISENGAGEDPOSITION AT A SPEED WHEREBY RECOVERY VOLTAGE AT ANY INSTANT ISINSUFFICIENT TO CAUSE BREAKDOWN FROM SAID MOVABLE CONTACTS TO SAIDSTATIONARY CONTACTS; AND AN INSULATING BARRIER MEANS; SAID INSULATINGBARRIER MEANS BEING INTERPOSED BETWEEN SAID PAIR OF STATIONARY CONTACTSWHEN SAID MOVABLE BRIDGING CONTACT IS MOVED TO SAID DISENGAGED POSITION;SAID PAIR OF STATIONARY CONTACTS BEING RELATIVELY CLOSELY SPACED WITHRESPECT TO ONE ANOTHER RELATIVE TO THEIR REQUIRED SPACING IN THE ABSENCEOF SAID INSULATING BARRIER WHEREBY THE MASS OF SAID MOVABLE CONTACT ISDECREASED; SAID MOVABLE BRIDGING CONTACT BEING CARRIED BY SAIDINSULATING BARRIER; A SPRING BIASING MEANS; SAID SPRING BIASING MEANSBEING OPERATIVELY CONNECTED TO SAID INSULATING BARRIER FOR BIASING SAIDMOVABLE CONTACT TOWARD SAID ENGAGED POSITION AND FOR PROVIDING CONTACTPRESSURE; SAID SPRING BIASING MEANS BEING CHARACTERIZED IN HAVING ITSBIASING FORCE SHARPLY DECREASED TO ZERO IMMEDIATELY AFTER MOVEMENT OFSAID MOVABLE BRIDGING CONTACT TOWARD ITS SAID DISENGAGED POSITION.